The overall objective of the proposed project is to further our understanding of CNS neurogenesis by analyzing the differentiation and morphological interaction of the 6 major cell types of the mouse retina (photoreceptor, bipolar, horizontal, amacrine, ganglion and Muller cells). The powerful technique of electron microscopic serial sectioning and reconstructions, as recently applied successfully to early ganglion cell development, will be employed. Long series of serial sections (400- 500 sections) will be cut, photographed in an electron microscope, and used to graphically reconstruct entire cells. By careful selection of stages to be analyzed in detail, it will be possible to identify cell types early in their development and arrange transitional forms into a sequence of differentiation for each of the 6 cell types. Specific objectives include: (1) determination of the earliest changes in the differentiation of each of the 6 cell types from proliferative ventricular cells; (2) discovery of information about the state of certain retinal cells during the latent period that occurs after final cell division but before obvious morphological differentiation; (3) determination of the relationship between the formation of dendritic and axonal arborization for the 5 neuronal cell types; (4) obtaining of qualitative and quantitative information on cell organelle development for the 6 cell types; (5) analysis of cell- to-cell relationships between cells from their final cell division through to the formation of specific synapses.